Xie Zhengqiang is no stranger to death but he trembles every time he thinks about his nephew. When doctors diagnosed three-month-old Xie Yuling with a rare auto-immune disease in 2011, the baby’s father was out sea crab fishing, so Xie was sent to the Shanghai hospital where his nephew was undergoing treatment. Three times a week he cycled alone past his fishing village’s tucked-away tangle of concrete-hulled houseboats, past the miles of adjacent chemical, pharmaceutical and power plants, and down along the burbling Yangtze river, where his family collects drinking water.

Then one day, he got the call. “The doctor tried everything to make him better, but he didn’t get better, and he died,” said Xie, 24, gazing up at the paper mill which towers above his home. “It was definitely the pollution. What else could it have been?”

Yanglingang residents count their home as one of China’s “cancer villages” – small communities near polluting factories where cancer rates have soared far above the national average. Chinese media, academics and NGOs estimate that the country is home to 459 of them, spread across every province except far-western Qinghai and Tibet.

New cases seem to emerge monthly, each a painful reminder that China’s past three decades of breakneck economic growth have carried a tremendous human cost. Yanglingang is home to only a few hundred people and at least 11 have died of cancer since 2003. Xie’s neighbour, Liu Shudong, is dying of oesophageal cancer. Another neighbour, Wang Jinlan, died of breast cancer in 2010. Last year, stomach cancer claimed his friend’s 30-year-old wife.

In February, the ministry of environmental protection mentioned cancer villages in its latest five-year plan – the only ministry-level acknowledgement of the issue since it was first reported in 1998. Chinese NGOs and activists hailed the report as a much-needed step towards environmental transparency. Yet interviews in three cancer villages across two provinces revealed that many central and local authorities continue to treat the issue as they long have: with denial, intimidation and silence. Even the environmental ministry’s acknowledgement was a mistake, said Chen Wanqing, deputy head of China’s national cancer registry. The ministry has been reprimanded.

Health and environmental officials organised a joint meeting during the National People’s Congress, a political gathering in March to renounce the report’s wording.They sent missives to provincial officials urging them to restrict usage of the term in local media. “This is a medical issue – it can’t be acknowledged from outside the ministry of health,” Chen said. “The statement was not correct, or not appropriate.”

However, the link between pollution and poor health is well established. Cancer mortality rates in China have risen 80% over the past 30 years, making it the country’s leading cause of death. In cities, toxic air is a primary suspect; in the countryside, it’s the water. More than 70% of the country’s rivers and lakes are polluted, according to government reports; almost half may contain water that is unfit for human contact.

“Fundamentally, the situation isn’t getting any better,” said Liu Lican, a Guangzhou-based journalist who has published a book about cancer villages. Pollution-related cancer, he said, can elude detection for years. “So even if the cancer was caused by pollution that’s already gone, maybe gradually more and more of these villages will emerge.”

Yanglingang lacks a public water supply, and before the government built the industrial zone in the early 2000s, the villagers didn’t mind; the river was clean, its fish abundant. But for eight years, Yanglingang has been sandwiched between the Nine Dragons paper mill and a power plant that billows white smoke from four tall stacks, covering the houseboats in a thin layer of ash. The mill discharges its wastewater directly into the Yangtze, leaving a maroon residue on the rocks along its shoreline.

Villagers purify the water with alum powder before drinking it, but even well-treated batches carry a faint industrial aftertaste. “Everybody here has some form of illness,” Xie said. His mother is bedridden with bronchitis. His infant nephew died of Evans syndrome, which has no known cause but is not usually fatal. The family took out £7,000 in loans to pay for the baby’s medical expenses, and Xie doubts that they will ever be repaid.

Despite abundant anecdotal evidence for China’s profusion of cancer villages, scientific proof has been elusive. When Wu Yixiu, toxics campaigner at Greenpeace East Asia, first visited Yanglingang in 2010, she assumed that establishing a causal connection between its pollution and cancer problems would be fairly straightforward – its population is so tiny, the disease so widespread, the pollution so caustic. “It’s unimaginable that their health will not be affected by the quality of this water,” she said.

Yet there are too many specific chemicals involved and too many types of cancer; diagnoses are spread over too many years. “You need to establish the fact that it’s a certain chemical that’s causing certain cancers, and this chemical is being discharged from this very factory,” she said. “This would require years of observation and tracing disease records.”